The present invention relates to a method of monitoring the physiological condition and/or suitability of animal feed of ruminant animals, comprising:                a. sensing the occurrence of at least one predetermined type of activity of the animal;        b. determining information about a time period of the first type which corresponds with the duration of the at least one predetermined type of activity which is detected in step a.;        c. repeating steps a. and b. for next sensed occurrences of activities of the at least one predetermined type;        d. transmitting the information determined in steps b.        
Such a method is known from U.S. Pat. No. 7,350,481.
In the known method the at least one predetermined type of activity is chewing. The chewing action is measured by means of a sound sensor. Use is made of a data processor for accumulating both the time of each of said sensed chewing actions and the number of such chewing actions per unit time interval, for determining the chewing rhythm of the animal indicating rumination activities over a predetermined time period. The information determined by the data processor is subsequently transmitted by means of a transmitter towards a remote receiver.
A disadvantage of the known method is that the content of the transmitted information may be incomplete because data may be lost.